1. Field of the Invention
The present invention relates to a semiconductor device having a temperature detecting function to optimize the acting state in accordance with a detected temperature detected with little dispersion, so as to achieve a sufficient acting performance over the entire working temperature range including a lower temperature region and a higher temperature region and, more particularly, to an improvement in the acting performance in a semiconductor storage device.
2. Description of Related Art
Generally, a semiconductor device element constructing a semiconductor device has temperature characteristics, and a semiconductor device constructed by integrating the semiconductor device elements has temperature characteristics from its acting characteristics. Moreover, the semiconductor device is generally employed in a predetermined temperature range and is demanded to have predetermined temperature characteristics for the entire working temperature range.
FIG. 27 illustrates a consumed current IDD and various action speeds tACCESS, i.e., representative acting characteristics against the temperature for a semiconductor device constructed of CMOS device elements. Generally in the semiconductor device constructed of CMOS device elements, as illustrated in FIG. 27, the action speed tACCESS becomes the lower at the higher temperature, and the consumed current IDD becomes the higher at the lower temperature. The individual acting characteristics are warranted under the worst conditions so that the various acting speeds tACCESS are warranted (at (A) in FIG. 27) with the maximum tmax in the working temperature range, and the consumed current IDD is warranted (at (B) in FIG. 27) with the minimum tmin in the working temperature range. As a result, the specifications on the acting characteristics in the entire working temperature range (from tmin to tmax) are warranted.
For a semiconductor memory representing the semiconductor device constructed of CMOS device elements, the internal construction (FIG. 28) and the temperature characteristics (FIG. 29) of the construction are shown in FIGS. 28 and 29. Here are illustrated the temperature characteristics on the refresh control of a semiconductor memory 100 requiring the refresh action, such as a dynamic random access memory (as will be abbreviated into xe2x80x9cDRAMxe2x80x9d) of the semiconductor memory.
In the prior art, as shown in FIG. 28, the semiconductor memory 100 is controlled on a refresh period tREF of a memory cell 102 by a refresh control circuit 101. In the memory cell 102, as illustrated in FIG. 29, the leakage current increases with the rise in the temperature so that the data holding characteristics are deteriorated by the electric charge to exhibit the negative temperature characteristics in which a data holding time tST is shortened.
On the other hand, the refresh period tREF to be set by the refresh control circuit 101 is set by an oscillation circuit such as a ring oscillator. According to the temperature characteristics of the various action speeds tACCESS of CMOS device elements, however, the action speeds tACCESS are raised the higher at the lower temperature. As a result, there is a tendency in which the positive temperature characteristics appear for the working temperature (at (II) in FIG. 29). With the setting (at (I) in FIG. 29) of the refresh period tREF to cross the data holding time tST in the working temperature range, there exists a temperature region (at (C) in FIG. 29) in which the refresh period tREF is longer than the data holding time tST, so that the data in the memory cell 102 undesirably disappear.
It is, therefore, customary to set the refresh period tREF (at (II) in FIG. 29) to cross the data holding time tST at a temperature exceeding the maximum tmax in the working temperature range. As a result, the refresh action is done for the refresh period tREF shorter than the data holding time tST in the entire working temperature range (from tmin to tmax), so that the data stored in the memory cell 102 do not disappear.
In the semiconductor device exemplified by CMOS device elements, however, the action warranty of the consumed current IDD and the various action speeds tACCESS are regulated by the minimum tmin and the maximum tmax in the working temperature range other than the ordinary one, so that the system employing the semiconductor device is designed/manufactured on the basis of the warranting values. Therefore, a fear and a problem arise in that the system sufficiently utilizing the acting performance of the semiconductor device in the ordinary working temperature region cannot be constructed.
In the semiconductor memory 100, moreover, the refresh period tREF to be set in the lower temperature region of the working temperature range is set excessively short (at (D) in FIG. 29) due to not only the negative temperature characteristics of the data holding time tST but also the positive temperature characteristic tendency of the refresh period tREF. Therefore, the refresh control circuit 101 performs the refresh actions for a sufficiently shorter time than the data holding time tST of the memory cell 102 and in an excessive frequency more than necessary. The current consumption accompanying the excessive refresh action is so surplus that the consumed current IDD in the lower temperature region cannot be sufficiently reduced to raise a problem that the action characteristics of the consumed current IDD warranted with the minimum tmin in the working temperature range cannot be improved.
Especially in a mobile device in which the semiconductor memory 100 is ordinarily employed at a temperature lower than the room temperature, the continuous employing time by the battery drive is restricted to raise a problem by the consumed current IDD accompanying the excessive refresh action in a temperature region lower than the room temperature.
The present invention has been conceived to solve the above-specified problems of the prior art and has an object to provide a semiconductor device having a temperature detecting function to detect a predetermined temperature with little dispersion and to optimize the acting state in accordance with the predetermined temperature detected, a testing method, and a refresh control method of a semiconductor memory device having the temperature detecting function.
In order to achieve the object, according to one aspect of the present invention, there is provided a semiconductor device having a temperature detecting function, comprising: a temperature detecting unit for detecting a predetermined temperature; and a voltage biasing unit for outputting a predetermined voltage having a slight temperature dependency or a predetermined voltage having a predetermined temperature dependency, to bias the temperature detecting unit.
In the semiconductor device having the aforementioned temperature detecting function, the temperature detecting unit for detecting the predetermined temperature is biased with either the predetermined voltage having the slight temperature dependency or the predetermined voltage having the predetermined temperature dependency, as outputted from the voltage bias unit.
With the temperature dependency of the predetermined voltage for biasing the temperature detecting unit being slight, therefore, the generally constant predetermined voltage is biased as the DC characteristics to the temperature detecting unit so that the detecting precision of the temperature detecting unit can be improved. The predetermined temperature to be detected is not fluctuated by the fluctuations of the bias voltage so that the temperature can be stably detected. If the predetermined voltage for biasing the temperature detecting unit has the predetermined temperature dependency, moreover, the fluctuations of the temperature to be detected can be in the temperature direction margin for the predetermined temperature so that the temperature can be stably detected.
According to another aspect of the present invention, moreover, there is provided a semiconductor device having a temperature detecting function, comprising: a temperature detecting unit for detecting a predetermined temperature; a first voltage biasing unit for outputting a first voltage to bias the positive supply side of the temperature detecting unit; and a second voltage biasing unit for outputting a second voltage dropped by a predetermined voltage from the first voltage biasing unit, to bias the negative supply side of the temperature detecting unit, wherein the temperature detecting unit is biased with the predetermined voltage.
In the semiconductor device having the aforementioned temperature detecting function, the first voltage is applied to the positive supply side of the temperature detecting unit, and the second voltage is applied to the negative supply side so that the voltage difference between the positive supply side and the negative supply side is kept at the predetermined voltage.
As a result, the first voltage to be applied to the positive supply side of the temperature detecting unit and the second voltage to be applied to the negative supply side keep the voltage difference of a predetermined voltage so that the predetermined voltage is biased as the DC characteristics between the positive/negative supply sides of the temperature detecting unit. If the equivalent in-phase transient responsive output characteristics are given as the voltage difference between the first and second voltages, moreover, the voltage difference at the predetermined voltage can be kept as the transient responsive characteristics. The predetermined voltage is always biased between the positive/negative supply sides of the temperature detecting unit so that the temperature can be stably detected without any fluctuation of the predetermined temperature to be detected, as might otherwise be made by the bias voltage.
According to one aspect of the present invention, moreover, there is provided a method for testing a semiconductor device having a temperature detecting function, comprising: a testing temperature detecting step of detecting a testing temperature at a temperature characteristic testing time; an error measuring step of measuring an error quantity of the detected result of the testing temperature; and a correction step of correcting a temperature detecting unit for detecting a predetermined temperature, on the basis of the measured error quantity.
According to the testing method for the semiconductor device having the aforementioned temperature detecting function, the error quantity of the detected result of the testing temperature at the temperature characteristic testing time is measured to make the correction of the temperature detecting unit for detecting the predetermined temperature on the basis of the error quantity.
As a result, the detection of the testing temperature is done by the temperature characteristic tests of the prior art, and the error quantity from the actual testing temperature is measured so that the temperature detecting unit for detecting the predetermined temperature can be relatively corrected on the basis of the error quantity. Without any temperature detecting test at the predetermined temperature to be detected by the predetermined temperature detecting unit or the temperature detecting unit, the temperature detecting unit can be relatively corrected to shorten the testing time thereby to compress the testing cost.
According to another aspect of the present invention, moreover, there is provided a method for testing a semiconductor device having a temperature detecting function, comprising: a testing temperature detecting step of making at least two kinds of detections of a testing temperature, the detection of a first near temperature having a slight detecting temperature difference on a higher temperature side with respect to the testing temperature and the detection of a second near temperature having a slight detecting temperature difference on a lower temperature side, at a temperature characteristic testing time; an error measuring step of measuring the difference till the detected results of the two end temperatures of the at least two kinds of detections are contrary to each other, as a detection error; and a correction step of correcting a temperature detecting unit for detecting a predetermined temperature on the basis of the measured error quantity.
According to the testing method of the semiconductor device having the aforementioned temperature detecting function, at the time of detecting the testing temperature at the temperature characteristic testing time, there are obtained at least two temperature detecting results which are selected from the testing temperature and the first and second near temperatures across the testing temperature. Moreover, the difference till the detection results of the two end temperatures are contrary to each other is measured as the detector error, and the temperature detecting unit for detecting the predetermined temperature is corrected on the basis of the error quantity.
As a result, the testing temperature is detected at the temperature characteristic tests of the prior art, and the error quantity from the actual testing temperature is measured, so that the temperature detecting unit for detecting the predetermined temperature can be relatively corrected on the basis of the error quantity. Without any temperature detecting test at the predetermined temperature detecting unit or the predetermined temperature to be detected at the temperature detecting unit, the temperature detecting unit can be relatively corrected to shorten the testing time thereby to compress the testing cost.
Moreover, the testing temperature or at least two temperatures having the slight temperature difference selected from the near temperature are detected so that the testing temperatures are confined within the slight temperature difference while the two detected results being contrary to each other. By adjusting the slight temperature difference, the detecting precision of the testing temperature can be adjusted to adjust the precision of the error quantity of the detected results thereby to correct the temperature detecting unit relatively in a high precision.
Moreover, it is possible to judge to which of the higher temperature side/lower temperature side the detected results are shifted with respect to the actual testing temperature thereby to execute the correcting procedure efficiently.
According to one aspect of the present invention, moreover, there is provided a refresh control method of a semiconductor storage device having a temperature detecting function, wherein the period of a refresh action is switched according to a detected temperature detected by a temperature detecting unit.
In the refresh control method of the semiconductor storage device having the aforementioned temperature detecting function, the period of the refresh action is switched according to the temperature which is detected by the temperature detecting unit.
As a result, the refresh action can be made for the period matching the holding characteristics of the stored charge of the memory cell having the temperature dependency, to hold the data over the wide temperature range, and the refresh action more than necessary can be suppressed to reduce the consumed current accompanying the refresh action.
The above and further objects and novel features of the invention will more fully appear from following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.